The fire burned through the night and into the following day. By the morning of 3 January, emergency crews were still damping hotspots throughout the complex, and that afternoon the fire broke out again on the roof of the National Assembly building, completing the destruction of a structure that had already been severely compromised. The new National Assembly building suffered the worst damage, but the old National Assembly building also lost offices and its gymnasium to flames, water, and smoke. In a rare piece of relief, the complex's important works of art and heritage items were reportedly found intact -- sculptures, paintings, and historical documents that had survived not because of any particular protective measures but because the fire's path happened to spare the rooms that housed them.

Within hours of the fire, the South African Police Service's Directorate for Priority Crime Investigation -- the Hawks -- arrested a 49-year-old man named Zandile Christmas Mafe. He was charged with arson, housebreaking, and theft under the National Key Points Act, legislation that designates certain buildings as critical infrastructure. After a brief appearance in the Cape Town Magistrates' Court, Mafe was remanded into custody. The prosecution revealed he had been diagnosed with paranoid schizophrenia, and the state sought to have him committed for 30 days of observation to determine whether he was fit to stand trial. On 29 January, the State alleged that Mafe had confessed to starting the fire, stating in an affidavit that he believed it was "the right thing" to burn parliament in order to prevent President Cyril Ramaphosa from delivering the State of the Nation Address.

The City of Cape Town released a preliminary report on 6 January that confirmed what firefighters had already suspected: systemic maintenance failures had allowed the fire to spread far beyond what a functioning building should have permitted. The National Assembly's sprinkler valve system had not been serviced since 2017 and was closed at the time of the fire -- meaning the sprinklers never activated. Fire doors, designed to compartmentalize a blaze and slow its spread, had been latched open. Protection services staff were not on duty when the fire started, and the CCTV system was not being monitored in the hours leading up to the blaze. The report painted a picture of a building whose safety systems had been allowed to decay through years of neglect, turning what might have been a contained incident into a catastrophic loss.

The fire forced South Africa's legislature to improvise. On 7 January, National Assembly Speaker Nosiviwe Mapisa-Nqakula and National Council of Provinces Chairperson Amos Masondo announced that President Ramaphosa's State of the Nation Address would move to Cape Town City Hall, where 300 Members of Parliament and 70 guests would gather under COVID-19 capacity restrictions. Regular National Assembly sittings, including the Finance Minister's Budget Speech, were relocated to the Good Hope Chamber -- one of the oldest meeting rooms in the parliamentary complex, originally the meeting place of the Parliament of the Cape of Good Hope from 1854 to 1885. The chamber seats only 170, a constraint that forced tight scheduling. The rebuilding was estimated at R2 billion and two years of work, with the Development Bank of Southern Africa appointed as project lead in March 2023.